1. Field of the Invention
The present invention relates to a method to form an optical grating and to form a distributed feedback laser diode providing the optical grating.
2. Related Prior Art
It is well known in the field of the semiconductor process that, what is called as the nano-imprint technique, pushing a silica mold with a predetermined pattern on a resin; this pattern may be transcribed on the resin. The United States patent, U.S. Pat. No. 7,165,957 has disclosed such nano-imprint technique.
In the conventional nano-imprint technique, one mold with a specific periodic pattern transcribes its pattern on the surface of the resin, that is, the mold may determine only one pattern. When semiconductor devices are necessary to provide their specific patterns, in particular, when the devices provide gratings with pitches specific to independent devices, the number of molds equal to the number of devices is necessary to be prepared.
The present invention is to solve the subject above, that is, one mold of the nano-imprint method is applicable to only one device, the mold according to the present invention is adjustable in the pitch thereof for various devices with a grating specific to the device.